This application claims the benefit of Korean Patent Application No. 1999-13183, filed on Apr. 14, 1999, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a reflective liquid crystal display, and more particularly to an auxiliary light source unit for radiating light onto a reflective liquid crystal display.
2. Discussion of the Related Art
A liquid crystal display (LCD) is a flat panel display device having advantages of small bulk, thin thickness and low power consumption. LCDs have been used in connection with portable computer devices such as notebook personal computers, office automation equipment and audio/video machinery, etc. LCDs control an electric field applied to a liquid crystal material having a dielectric anisotrophy to transmit or shut off a light, thereby displaying a picture or an image. LCDs use an external light source, unlike display devices that generate light internally, such as an electro-luminescence (EL) device, a cathode ray tube (CRT), a light emitting diode (LED) and so on.
LCD devices are largely classified into transmissive type devices and reflective type devices, depending on the method of utilizing light. The transmissive type LCDs includes a liquid crystal panel having a liquid crystal material injected between two transparent substrates and a backlight unit for supplying light to the liquid crystal panel. However, it is difficult to make a transmissive LCD with thin thickness and light weight. Moreover, the backlight units of transmissive LCDs have excessive power consumption.
On the other hand, reflective type LCDs include a reflective liquid crystal display panel 10 that transmits and reflects natural light and peripheral light to and from the display screen without a backlight unit. As shown in FIG. 1, reflective liquid crystal panel 10 consists of a liquid crystal panel 2 in which a liquid crystal material is injected between two transparent substrates and a reflector 4 arranged at the rear side of the liquid crystal panel 2 or arranged at the interior of the liquid crystal panel 2 to reflect a light toward the viewing side. This reflective LCD reflects natural light or peripheral light by means of the reflector 4 to display a picture or an image. However, the reflective LCD has a considerably low brightness level when the natural light or peripheral light is not sufficient. In order to solve this problem, there has been suggested a reflective LCD using auxiliary light source other than natural light.
FIG. 2 shows a reflective LCD employing a point light source disclosed in the magazine, Nikkei Electronics Asia, published in July 1998. Referring to FIG. 2, the conventional reflective LCD includes a reflective liquid crystal panel 12, a support bar installed at one side of the reflective liquid crystal panel 12, and an auxiliary light source 16 as a point light source installed at the edge of the support bar 14. The auxiliary light source 16 radiates light onto the reflective liquid crystal display panel 12 from a certain distance by means of the support bar 14. Because the auxiliary light source 16 of the reflective LCD has a point light source and because the support bar 14 is installed at the comer of the reflective liquid crystal panel 12, the incidence angle of the light provided by the auxiliary source on the display screen is different at every incident position. Thus, the quantity of light at each incident position differs considerably on the reflective LCD device. Accordingly, the brightness of the reflective LCD is non-uniform because the LCD is not illuminated with a uniform quantity of light.
FIG. 3 shows a reflective LCD disclosed in U.S. Pat. No. 5,477,239. Referring to FIG. 3, the conventional reflective LCD shown includes a display module 24 pivotally attached to a main body. The display module 24 houses a reflective liquid crystal display panel 22 and auxiliary light sources 26a and 26b. Auxiliary light sources 26a and 26b are line light sources at the left and right sides of the reflective liquid crystal display panel 22. Each auxiliary light source 26a and 26b is installed in such a manner to be opened and closed on the display module 24. Each auxiliary light source 26a and 26b radiates light onto the surface of the reflective liquid crystal display panel 22. A film (not shown) is adhered to an upper glass substrate of the reflective liquid crystal display panel 22. This film includes a number of minute structures for reflecting light received from the auxiliary light sources 26a and 26b toward the display screen of the reflective liquid crystal display panel 22. Each of the minute structure must have a different inclination angle and height so that a light can be uniformly received at the display screen of the reflective liquid crystal display panel 22. The minute structures are difficult to design and to fabricate because of the plurality of inclination angles required. Moreover, because additional area is required for the display module 24 to house the auxiliary light sources 26a and 26b, the effective display area of the liquid crystal display panel 22 is reduced and the display module 24 is enlarged. Light incidence efficiency is low because the quantity of light incident to the reflective liquid crystal display panel 22 at different positions depends upon the distance from the auxiliary light sources 26a and 26b to each position on the liquid crystal display panel 22.
FIG. 4 shows a reflective LCD disclosed in U.S. Pat. No. 5,091,873. Referring to FIG. 4, the conventional reflective LCD includes a display module 34 pivotally attached to a main body 38 and mounted with a reflective liquid crystal display panel 32, and a light source 40 mounted releasably on the main body 38. The light source 40 includes a lamp 42 for generating light and a reflector 44 for reflecting light radiated from the lamp 42 toward the reflective liquid crystal display panel 32, thereby radiating light onto the display screen of the liquid crystal display panel 32. However, the reflective LCD increases the bulk of the main body 38, and the light source 40 complicates the structure.
As described above, in conventional reflective LCDs, it is difficult for light to be uniformly radiated onto the display screen, because of the location of the auxiliary light source. Moreover, it is difficult to make a product using a conventional reflective LCD that is light weight and small in dimension because of the need for an auxiliary light source.
Accordingly, the present invention is directed to an auxiliary light source unit for reflective liquid crystal display (LCD) that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an auxiliary light unit for a reflective liquid crystal display that is adapted to radiate light uniformly.
A further object of the present invention is to provide an auxiliary light unit for a reflective liquid crystal display that permits the liquid crystal display to be light weight and small in dimension.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an auxiliary light source apparatus for a reflective liquid crystal display according to an embodiment of the present invention includes a main body; a reflective display module installed pivotally at the main body; a support member opened and closed from and to the main body in opposition the reflective display module; and an auxiliary light source installed at the support member to radiate light onto the display area of the reflective display module.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.